1. Field of the Invention
The invention relates generally to devices for controlling the operation of various components of glassware forming machines. More specifically, the invention relates to a system for controlling the delivery of gobs of molten glass to sections of a glassware forming machine.
2. Description of the Prior Art
Prior art glassware forming machines of the individual section type form glassware from gobs of molten glass by the cyclic performance of a predetermined series of steps in each section of the machine. Each section generally contains one or more sets of blank molds for receiving one gob per set, means for performing a predetermined series of steps prior to transferring a parison to one or more corresponding sets of blow molds within that section and means for performing another predetermined series of steps to form a final article of glassware. Each section periodically performs an identical series of steps although sequentially in a predetermined firing order at phased times within the cycle of operation of the machine. In single gob machines, one gob is periodically distributed to each section which then produces one glassware article therefrom. In double gob machines two gobs are simultaneously distributed to each section which contains two sets of molds and associated components for producing one glassware article from each gob. Triple gob machines also exist in the prior art.
These glassware forming machines generally operate in conjunction with a cyclically oscillating gob distributor for periodically and sequentially distributing one or more gobs of molten glass to each section, a feeder serving as a source of one or more streams of molten glass, shears for cutting each stream into gobs and an interceptor associated with each stream and interposed between the shears and the gob distributor for occasionally, as needed, intercepting the gobs to reject them and prevent them from passing to the distributor and on to a particular section. While the interceptor is sometimes considered as part of the gob distributor, as used herein it will be considered a separate mechanism.
The interceptor is normally held retracted out of the way to enable the gobs to pass to the gob distributor. The motion of the interceptor between a retracted delivery position allowing the gobs to pass, and an extended intercept position, rejecting gobs to a cullet chute, is controlled by a delivery enable pulse signal associated with each section of the glassware forming machine. The delivery enable pulse of a particular section is turned on at one predetermined point of the machine cycle and off at another predetermined point. During the on time a gob may be delivered to that section. Those skilled in the art will understand that gob delivery to that section at any other time must not occur because the section will be performing various other functions in order to produce finished glassware and will not be able to accept any gob. Prior art glassware forming machine control systems have attempted to solve the problem of inadvertent delivery of a gob (to a section not ready to accept it) by moving the interceptor to intercept the gob during all times of a section's cycle except during the on time of that section's delivery enable pulse.
The timing controller associated with each section outputs a delivery enable pulse to the interceptor during a predetermined time in that respective section's cycle. The delivery enable pulses from successively phased sections occur sequentially to prevent interference between sections. The net effect could be that the interceptor would oscillate between intercept and delivery positions once during each section cycle. As a practical matter the delivery enable pulses are sufficiently long to abut each other in time to prevent such oscillation, thus saving wear and tear on the mechanical interceptor. In a 10-section machine, for example, each delivery enable pulse will be 36.degree. wide (with respect to the machine cycle) which will produce a continuous level signal to the interceptor in order to prevent it from oscillating. Each section produces a 36.degree. wide delivery enable pulse, all of the pulses abutting to produce this continuous level signal. While delivery of the gob is not theoretically possible at all times during this 36.degree. period because of the occasional interference and motion of various components within the section, it is, nevertheless, desirable not to have the interceptor oscillate. Because of the continuous level signal there is the possibility that a gob may be delivered to a section at a point in time when the section is unable to accept it.
Even if there was no continuous level signal and the interceptor oscillated between the intercept and delivery positions there is the possibility that a delivery enable pulse from one section may occur at an improper time and cause the interceptor to be held in the delivery position while the gob was being delivered to another, inactive section. There is a need in the prior art for an apparatus to monitor the delivery enable pulses of the various sections to assure that the pulse from one section does not enable gob delivery to another section that is inactive or is otherwise unable to receive the gob.
Furthermore, since the operation of the gob distributor is synchronized to operation of the machine rather then to any individual section, there is a possibility that gobs may be continued to be delivered to various sections of the machine if the interceptor is not in the intercept position. Thus, there is a need for a device to monitor the position of the interceptor to shut down delivery of gobs to all sections if the interceptor has been commanded to go to but is not in the intercept position. If the interceptor has been commanded by, for example, the absence of a delivery enable pulse from a section that has been shut down for maintenance, swabbing, etc., the interceptor must move to the intercept position or else molten glass may be delivered to the inactive section with hazardous consequences. Since such a failure of the interceptor is very serious, safety measures must be taken to prevent gob delivery to all sections until the problem is corrected.
Prior art electronic or other control systems do not perform any gob delivery control function or interceptor monitoring function. Relevant prior art control systems include non-programmable electronic control means individual to each section (U.S. Pat. No. 3,762,907); a programmable machine controller utilizing storage means for storing the times when machine components are to be actuated, and comparator means for comparing the cycle time with the component actuating times to provide actuating signals upon positive comparison (U.S. Pat. No. 3,969,703); a programmable controller utilizing machine supervisory control means to load program and timing data into a storage means associated with each section (U.S. Pat. No. 4,152,134); a programmable section controller utilizing storage means for storing signals corresponding to the on/off status of component parts (U.S. Pat. No. 4,247,317); and a method and aparatus for performing a predetermined series of steps to freeze a parison for examination purposes (U.S. Pat. No. 4,141,711).